There is a fundamental gap in understanding how exogenous hydrocarbons can interfere with key signaling pathways critical for pleiotropic drug response (PDR) and other critical biochemical pathways important for cellular signal ling. Persistence of this gap in knowledge represent an important problem because some people were exposed to 4-methylcyclohexane methanol (MCHM) and had immediate unexplained health problems. Long-term health problems are challenging to predict without obtaining this information. The long- term goal is to identify proteins that mediate phenotypic variation in response to toxic chemicals so that predictors of genotypes of individuals, both yeast and humans, with increased sensitivity to environmental stressors can be established. The objective in this application is to determine cellular pathways that are affected by MCHM. Using Saccharomyces cerevisiae as a model organism, exposure to MCHM activated the pleiotropic drug response and down-regulated biosynthetic pathways responsible for making second messengers. The central hypothesis is that sub-lethal MCHM exposure will alter cellular pathways including the inositol and PDR pathways. This hypothesis was formulated based on preliminary data showing that S. cerevisiae exposed to MCHM significantly lagged in growth in comparison to unexposed cells. The rationale for this proposal is that a determination of the cellular effects of MCHM will provide a mechanism-based framework for subsequent detailed studies on MCHM's health effects in humans and further experiments with Xenopus tropicalis. The following specific aims are proposed: 1. Determine cellular pathways affected by MCHM and required for degradation of MCHM and 2. Assess the impact of variation in Med15 on MCHM response. Under the first aim we will monitor changes in cellular viability and transcriptional memory across yeast with different responses to MCHM. Under the second specific aim the focus will be on how genetic variation within Med15, an important and polymorphic transcriptional regulator changes the transcriptional and phenotypic response to MCHM measured by RNA-seq and proteomics respectively. The proposed research is innovative, in the applicant's opinion, because it represents a substantive departure from the status quo by assessing cellular responses using a systems approach including genetic, transcriptomic, and proteomic in genetically diverse yeast strains. This contribution will be significant because it will directly provide the foundation for determination of long-term effects f MCHM exposure on basic cellular function in a model organisms. In turn, this is likely to contribute to an understanding of potential human health long-term effects due to MCHM and other structurally similar but also understudied chemicals.